474 
]us be discovered in the corresponding serum at the end of six hours. 
This agrees with the number of colonies upon the agar plates. 
The heated serums gave quite a different picture under the micro- 
scope. Many organisms were found, lying singly, in small and long 
chains, and in dense clusters. This corresponded to the innumerable 
growth upon the agar plates. 
RELATION TO PHAGOCYTOSIS. 
Milk contains many leucocytes and it therefore seems reasonable 
to assume that active phagocytosis takes place in the fresh raw prod- 
uct. A priori it seemed to us that this might account for the germi- 
cidal property of milk. This assumption was apparently confirmed 
when we found that stained smear preparations showed but few if 
any bacteria in the cells in the fresh milk just after inoculation with 
bacterial cultures, while similar preparations made from the same 
milk eight hours later, kept at 37° C., showed numerous bacteria in 
some of the cells. 
The following experiments, however, demonstrate that the ger- 
micidal power of milk is independent of its cellular contents. The 
leucocyte- free milk is quite as active as the leucocyte-rich sediment 
obtained by centrifugation. 
Table No 15. 
[Milk from a healthy cow (No. 2) was centrifuged for twenty minutes at 1,500 revolutions 
per minute. Part of the supernatant fluid was passed through a Berkefeld filter and a 
clear bluish serum obtained. Five sets of tubes were inoculated with 24-hour agar 
cultures, (1) the filtered clear serum, (2) the supernatant fluid free from leucocytes,. 
(3) the sediment rich in leucocytes, (4) the original whole milk, and (5) sterilized milk. 
The inoculations were made three hours after milking.] 
_ o nours at 37 '-’ (j. 
Bacteria I 
per loop, — ; 
after inoc- Skaken , Vigoroi 
illation moderately agitatio 
uiation. befQre ( befQre 
planting, plantin, 
B. typhosus in filtered milk serum 
B. typhosus in leucocyte-free supernatant fluid 
B. typhosus in leucocyte-rich sediment 
B. typhosus in whole raw milk 
B. typhosus in sterilized milk (control) 
B. lactis aerogenes in filtered milk serum 
B. lactis aerogenes in leucocyte-free supernatant fluid 
B. lactis aerogenes in leucocyte-rich sediment 
B. lactis aerogenes in whole raw milk 
B. lactis aerogenes in sterilized milk (control) 
Original milk 
22,000 
19.000 
32.000 I 
3,500 
10,000 
1,900 
3,600 
1,200 
16.000 I ® & 160, 000 
33.000 3 & 330, 000 
4, 000 1 210 
42. 000 j 740 
5, 400 j 33 
36.000 i ® 6 360, 000 
19 
42 
15,000 
92 
a Innumerable. 6 About. 
This table also shows the effect/of shaking the milk in breaking up 
bacterial clusters. 
